U.S. patent number 7,321,009 [Application Number 10/482,656] was granted by the patent office on 2008-01-22 for process for the production of vermiculite foil.
This patent grant is currently assigned to Flexitallic Investments Incorporated. Invention is credited to John Robert Hoyes, Stephen Woolfenden.
United States Patent |
7,321,009 |
Hoyes , et al. |
January 22, 2008 |
Process for the production of vermiculite foil
Abstract
The invention is concerned with gasket sealing foils having a
sealing layer with enhanced properties which is based upon
chemically exfoliated vermiculite. The method of producing a
sealing foil for gaskets is described. The method comprises the
steps of: (a) the application of a wet sealing foil material to a
forming sheet to form a layer, (b) partially drying the said wet
sealing foil layer on the forming sheet; (c) removing the said
layer from the forming sheet to form a core free gasket sealing
foil; and (d) forming, preferably cutting, the layer into at least
one suitable shape for use in the formation of a gasket The sealing
foil comprises a resilient material, which comprises a CEV
component in a proportion of at least 25% w/w of the sealing foil,
the CEV component being at least partially derived from dry CEV.
The sealing foil layer may be combined with a gasket support layer
prior to or after the cutting step.
Inventors: |
Hoyes; John Robert
(Littleborough, GB), Woolfenden; Stephen (Rochdale,
GB) |
Assignee: |
Flexitallic Investments
Incorporated (Houston, TX)
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Family
ID: |
9917975 |
Appl.
No.: |
10/482,656 |
Filed: |
July 3, 2002 |
PCT
Filed: |
July 03, 2002 |
PCT No.: |
PCT/GB02/03062 |
371(c)(1),(2),(4) Date: |
June 16, 2004 |
PCT
Pub. No.: |
WO03/004578 |
PCT
Pub. Date: |
January 16, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20040214032 A1 |
Oct 28, 2004 |
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Foreign Application Priority Data
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Jul 5, 2001 [GB] |
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0116441.7 |
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Current U.S.
Class: |
524/442; 524/445;
524/448; 524/450; 524/444 |
Current CPC
Class: |
C04B
30/00 (20130101); C04B 14/208 (20130101); F16J
15/102 (20130101); C09K 3/10 (20130101); C09K
2200/0612 (20130101); C09K 2200/0265 (20130101) |
Current International
Class: |
C08K
3/34 (20060101) |
Field of
Search: |
;524/442,444,445,448,450 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2122699 |
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Jan 1984 |
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GB |
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WO 98/53022 |
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Nov 1998 |
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WO |
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WO 01/51834 |
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Jul 2001 |
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WO |
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Primary Examiner: Cain; Edward J.
Attorney, Agent or Firm: Haynes and Boone LLP
Claims
The invention claimed is:
1. A method of producing a sealing foil for gaskets comprising the
steps of: (a) the application of a wet sealing foil material to a
forming sheet to form a layer; (b) partially drying the said wet
sealing foil layer on the forming sheet; (c) removing the said
layer from the forming sheet to form a core free gasket sealing
foil; and (d) forming, preferably cutting the layer into at least
one suitable shape for use in the formation of a gasket; the
sealing foil comprising a resilient material, the resilient
material comprising a CEV component in a proportion of at least 25%
w/w of the sealing foil, the said CEV component being at least
partially derived from dry CEV.
2. A sealing foil for a gasket comprising a resilient material, the
resilient material comprising a CEV component in a proportion of at
least 25% w/w of the sealing foil, the said CEV component being at
least partially derived from dry CEV, the sealing foil not
including a core carrier material wherein the sealing foil is
suitable for forming, preferably cutting, into a suitable shape for
use in combination with a gasket support layer.
3. A method according to claim 1, wherein the sealing foil layer is
combined with a gasket support layer prior to or after the cutting
step.
4. Use of a sealing foil for a gasket, the said sealing foil
comprising a resilient material, the resilient material comprising
a CEV component in a proportion of at least 25% w/w of the sealing
foil, the said CEV component being at least partially derived from
dry CEV, the sealing foil not including a core carrier material, in
the manufacture of a gasket.
5. A method of manufacture of gasket comprising the steps of: (a)
applying a sealing foil comprising a resilient material, the
resilient material comprising a CEV component in a proportion of at
least 25% w/w of the sealing foil, the said CEV component being at
least partially derived from dry CEV, the sealing foil not
including a core carrier material to a support layer to form a
gasket material and, optionally, (b) forming, preferably cutting,
the gasket material to thereby form the required gasket shape.
6. A method according to claim 5, wherein the step (a) is preceded
by the step (c) of removal of the sealing foil from a forming
sheet.
7. A method according to claim 5, wherein step (b) is carried out
prior to step (c).
8. A method according to claim 1, wherein the sealing foil is at
least partially dry prior to use as a sealing foil.
9. A method according to claim 1, wherein the sealing strip has a
small moisture content during use in manufacture.
10. A method according to claim 1, wherein the sealing strip has a
small moisture content during removal from a forming sheet on which
the sealing foils are formed.
11. A gasket comprising a sealing foil comprising a resilient
material, the resilient material comprising a CEV component in a
proportion of at least 25% w/w of the sealing foil, the said CEV
component being at least partially derived from dry CEV, wherein
the sealing foil has a moisture level of between 3-20% w/w of the
sealing foil resilient material during manufacture of the said
gasket.
12. A method according to claim 1, wherein the solids content of
the wet sealing foil material is in the range 20-70% w/w of the wet
sealing foil material prior to partially drying the said wet
sealing foil layer on the forming sheet.
13. A method according to claim 1 wherein the wet sealing foil
layer material dough is dried at temperatures between
50-135.degree. C.
14. A method or gasket or sealing foil according to claim 1,
wherein the resilient layer comprises particles of gas-exfoliated
vermiculite.
15. A method or gasket or sealing foil according to claim 14,
wherein the material used may be milled or otherwise reduced in
particle size.
16. A method of producing a sealing foil according to claim 1,
wherein the sealing foil width is at least 10 cm.
17. A sealing foil for a gasket according to claim 2, wherein the
sealing foil width is at least 10 cm.
18. Use of a sealing foil for a gasket according to claim 4,
wherein the sealing foil width is at least 10 cm.
19. A gasket comprising: a sealing foil comprising: a resilient
material comprising a CEV component in a proportion of at least 25%
w/w of the sealing foil, the CEV component being at least partially
derived from dry CEV; a wet configuration in which: the resilient
material is adapted to be applied to a forming sheet; and the
sealing foil comprises a solids content in the range 20-70% w/w of
the sealing foil; and a partially-dried configuration in which: the
sealing foil comprises a moisture level of between 2-20% w/w of the
resilient material; and the resilient material is adapted to be
removed from the forming sheet.
20. A method of producing a sealing foil for gaskets, the sealing
foil comprising a resilient material, the resilient material
comprising a CEV component in a proportion of at least 25% w/w of
the sealing foil, the said CEV component being at least partially
derived from dry CEV, comprising the steps of: (a) the application
of a wet sealing foil material comprising a mixture of dried CEV
and CEV available in a slurry form to a forming sheet to form a
layer; (b) partially drying the said wet sealing foil layer on the
forming sheet; (c) removing the said layer from the forming sheet
to form a core free gasket sealing foil; and (d) forming,
preferably cutting the layer into at least one suitable shape for
use in the formation of a gasket.
21. A sealing foil for a gasket comprising a resilient material,
the resilient material comprising a CEV component in a proportion
of at least 25% w/w of the sealing foil, the said CEV component
being at least partially derived, during production of the gasket,
from dry CEV, the sealing foil not including a core carrier
material wherein the sealing foil is suitable for forming,
preferably cutting, into a suitable shape for use in combination
with a gasket support layer.
Description
The present invention is concerned with gasket sealing foils, in
particular, with foils having a sealing layer with enhanced
properties which is based upon chemically exfoliated vermiculite.
In addition, the invention relates to methods of manufacture and
use of the foil.
Exfoliated vermiculite is a known heat-resistant resilient
material. Exfoliated vermiculite is conventionally formed by
expanding mineral vermiculite using gas, this material being
referred to herein as "gas-exfoliated vermiculite". The gas may be
thermally generated, in which case the product is called
"thermally-exfoliated vermiculite" (TEV). TEV may be made by
flash-heating mineral vermiculite to 750-1000.degree. C., at which
temperature the water (free and combined) in the ore vaporises
rapidly and ionic repulsion forces apart the silicate sheets which
form the raw material, so bringing about an expansion of 10-20
times perpendicular to the plane of the sheets. The granules formed
have a chemical composition which (apart from the loss of water) is
virtually identical to that of the raw material. Gas-exfoliated
vermiculite may also be made by treating raw vermiculite with a
liquid chemical, eg hydrogen peroxide, that penetrates between the
silicate sheets and subsequently evolves a gas, eg oxygen, to bring
about exfoliation.
A different form of exfoliated vermiculite is known as
"chemically-exfoliated vermiculite" (CEV) and is formed by treating
the ore and swelling it in water. In one possible preparation
method, the ore is treated with saturated sodium chloride solution
to exchange magnesium ions for sodium ions, and then with n-butyl
ammonium chloride to replace sodium ions with
n-C.sub.4--H.sub.9NH.sub.3 ions. On washing with water swelling
takes place. The swollen material is then subjected to high shear
to produce an aqueous suspension of very fine (diameter below 50
.mu.m) vermiculite particles.
It is known to utilise exfoliated vermiculite as a layer of a sheet
gasket, eg an automotive exhaust gasket, and for other purposes.
For example, GB 2 193 953 B discloses forming sheet-like gaskets
formed from particles of gas-exfoliated vermiculite. Because such
particles do not cohere well, they are bound together by fine
particles of CEV. The use of CEV as a binder retains heat
resistance and resilience, whereas the use of other inorganic
binders could result in an incompressible structure. However,
although exfoliated vermiculite has excellent heat resistance and a
high degree of resilience, it has poor water resistance.
Furthermore, such products were manufactured using CEV with a high
water content at low solids content and considerable drying
problems are encountered during production due to the tendency of
CEV containing materials to form a surface skin which prevents the
further escape of moisture.
WO 98/53022 describes gaskets with a sealing layer and a support
layer. The sealing layer is formed from a resilient material which
comprises a CEV component in a proportion of at least 25% w/w of
the sealing layer. The CEV component is at least partially derived
from dry CEV. A hydrolysis resistant polymer to improve the water
resistance of the sealing layer is also provided in the proportion
of less than 20% w/w of the sealing layer.
A method of producing a gasket is also described. The method
involves applying a wet sealing layer dough to a support material,
and drying the wet sealing layer dough on the support material. The
support material forms a core for the sealing layer and provides a
support during the drying step. Spirally wound gaskets are also
described.
The sealing foil from which gaskets are commonly cut or otherwise
formed must have sufficient strength and flexibility to enable it
to be peeled from a forming sheet, packaged, stripped and processed
into a gasket without breakage. A sealing foil formed from expanded
graphite foil, although relatively brittle, does have sufficient
strength. However, in WO 98/53022 it is made clear that the sealing
layers described do not have sufficient strength to avoid breakage
during production of gaskets. Consequently, a carrier strip is used
to support the sealing layer during spiral wound gasket formation.
The other examples described in WO 98/53022 include a metal or
glass fibre core on which the sealing layer is formed.
It is an object of at least some of the preferred embodiments of
the present invention to provide a foil comprising a sealing layer
with improved water resistance and improved breakage resistance. It
is a further such object to provide a foil with a sealing layer
with reduced loss in stress retention and low creep. It is a
further such object of the present invention to provide a foil with
surprising improvements.
According to a first aspect of the present invention there is
provided a method of producing a sealing foil for gaskets
comprising the steps of: (a) the application of a wet sealing foil
material to a forming sheet to form a layer; (b) partially drying
the said wet sealing foil layer on the forming sheet; (c) removing
the said layer from the forming sheet to form a core free gasket
sealing foil; and (d) forming, preferably cutting the layer into at
least one suitable shape for use in the formation of a gasket; the
sealing foil comprising a resilient material, the resilient
material comprising a CEV component in a proportion of at least 25%
w/w of the sealing foil, the said CEV component being at least
partially derived from dry CEV.
According to a second aspect of the present invention there is
provided a sealing foil for a gasket comprising a resilient
material, the resilient material comprising a CEV component in a
proportion of at least 25% w/w of the sealing foil, the said CEV
component being at least partially derived from dry CEV, the
sealing foil not including a core carrier material wherein the
sealing foil is suitable for forming, preferably cutting, into a
suitable shape for use in combination with a gasket support
layer.
The sealing foil layer may be combined with a gasket support layer
prior to or after the cutting step.
According to a third aspect of the present invention there is
provided use of a sealing foil for a gasket, the said sealing foil
comprising a resilient material, the resilient material comprising
a CEV component in a proportion of at least 25% w/w of the sealing
foil, the said CEV component being at least partially derived from
dry CEV, the sealing foil not including a core carrier material, in
the manufacture of a gasket.
According to a fourth aspect of the present invention there is
provided a method of manufacture of gasket comprising the steps of:
(a) applying a sealing foil comprising a resilient material, the
resilient material comprising a CEV component in a proportion of at
least 25% w/w of the sealing foil, the said CEV component being at
least partially derived from dry CEV, the sealing foil not
including a core carrier material to a support layer to form a
gasket material and, optionally, (b) forming, preferably cutting,
the gasket material to thereby form the required gasket shape.
It is envisaged that the first step may be preceded by the step (c)
of removal of the sealing foil from a forming sheet. Alternatively,
step (b) may be carried out prior to step (c). Preferably, the
sealing foil of the present invention is at least partially dry
prior to use as a sealing foil.
Preferably, the resilient material also comprises a hydrolysis
resistant polymer to improve the water resistance of said sealing
strip, the proportion of the said polymer not exceeding 20% w/w of
the sealing strip.
Surprisingly, it has been found that the use of such levels of CEV
gives the sealing strip sufficient strength to be used in
manufacture of gaskets as a dry or semi-dry foil without the use of
a core material as a support whereas hitherto it had been expected
that the use of vermiculite rendered the sealing foil too brittle
for such purposes without the use of a core or carrier strip.
Preferably, the resilient material further comprises a plate like
filler material, preferably, a milled filler material.
Preferably, the sealing strip has a small moisture content during
use in manufacture and, preferably, during removal from a forming
sheet on which the sealing foils are formed.
Preferably, the moisture content sufficiently reduces the
brittleness of the foil or sufficiently increases the cohesion of
the foil to allow said manufacture and removal from the forming
sheet without damage, such as splitting or tearing, to the
foil.
For the avoidance of doubt, a gasket of the present invention may
provide conventional sealing between static or moving parts.
Preferably, the proportion of CEV is at least 30% w/w of the
sealing foil, more preferably at least 35% w/w of the sealing
foil.
Typically, the level of CEV falls within the range 25-80% w/w of
the sealing foil, more typically, 30-75% w/w of the sealing foil,
most typically 35-70% w/w of the sealing foil.
Preferably, the proportion of the said polymer is less than 15% w/w
of the sealing foil, more preferably, less than 10% w/w. Especially
preferred is a level of polymer less than 7.5% w/w, more especially
preferred is a level of polymer in the range 1.0-7.5% w/w of the
sealing foil.
The length of the sealing foil is one suitable for use in
subsequent processing. The foil may be flat packed or stored on
rolls. For instance, foils of length of more than 1 m may be used,
for example up to or greater than 5 m.
Preferably, the chemically exfoliated vermiculite component of the
present invention includes sufficiently dry CEV, to provide a wet
sealing layer dough with a reduced water content which is capable
of being dried before substantial skinning has occurred.
The term hydrolysis resistant polymer includes any suitable
elastomer such as silicon and carbon based elastomeric polymers.
Suitable polymers for use with the present invention include:
nitrile butadiene rubbers, styrene butadiene rubbers, natural
rubber, butyl rubber, siloxanes (particularly organosiloxanes such
as dialkyl siloxanes) and ethylene-propyldiene monomer. Diene-based
polymers are suitable because they are flexible and
hydrolysis-resistant.
The support layer for gasket manufacture may be made of any
suitable support material with which the sealing foil may be
combined to form the non-spirally wound gasket.
Suitable support layer materials include stainless steel and carbon
steel which may both be in the form of solid metal cores or thin
sheets. The solid metal cores may be suitably profiled or machined
to receive the sealing layer.
The thin sheets may be in the form of solid sheets, tanged sheet or
perforated sheet. Tanged sheet is especially preferred. Other
suitable support materials include:
wire mesh, such as expanded metal and woven gauze; fibre mesh, such
as glass fibre mesh; cloth; or a non woven material, such as
tissue.
According to a fifth aspect of the present invention there is
provided a gasket comprising a sealing foil comprising a resilient
material, the resilient material comprising a CEV component in a
proportion of at least 25% w/w of the sealing foil, the said CEV
component being at least partially derived from dry CEV, wherein
the sealing foil has a moisture level of between 3-20% w/w of the
sealing foil resilient material during manufacture of the said
gasket.
Preferably, the moisture level of the sealing foil during
manufacture is between 2-10% w/w of the resilient material of the
sealing foil, most preferably, 3-5% w/w.
Preferably, the sealing foil comprises 80% resilient material, more
preferably 90% resilient material, most preferably, it consists
substantially wholly of resilient material.
The sealing foil in accordance with this aspect of the invention
may or may not include a core material or carrier strip.
Preferably, the solids content of the wet sealing foil material
prior to the drying step of the first aspect is in the range 20-70%
w/w of the material.
It is also envisaged that the step (c) may be carried out after
step (d).
Preferably, the forming sheet is capable of withstanding drying
temperatures applied to the wet sealing foil layer. The forming
sheet may be stainless steel, a non-reactive polymer such as PTFE
or other suitable material to which the foil does not stick.
Preferably, the solids content of the said sealing foil layer is in
the range 25-60% w/w of the wet material, more preferably, 30-55%
w/w of the wet material, most preferably, 35-50% w/w of the wet
material.
Preferably, in accordance with any aspect of the present invention
the CEV is mixed with a suitable plate-like filling agent such as
thermally exfoliated vermiculite (TEV). Preferably, the filling
agent is milled. Preferably, the filling agent comprises less than
75% w/w of the sealing strip, more preferably, less than 70% w/w,
most preferably, less than 65% w/w of the sealing foil. Preferably,
the water content of the partially dried layer during removal from
the forming sheet is 3-20% w/w, more preferably 5-15%, most
preferably 7-13%. The forming sheet may be a moving belt which may
be continuous or not. In many cases the TEV content in the layer is
less than 55% w/w.
A further drying step may be carried out after removal of the
sealing layer foil material from the forming layer. Alternatively,
it may be allowed to air dry on the forming layer.
A wet sealing foil layer material dough in accordance with the
present invention may be dried at temperatures between
50-135.degree. C., more preferably, 60-130.degree. C., most
preferably, 80-125.degree. C. The material may also be allowed to
dry around room temperature but it is envisaged that this will be
difficult to commercialise.
Preferably, the wet sealing foil material is spread onto the
forming sheet using a suitable spreading technique such as the
application of a doctor blade. Calendering is also envisaged.
Preferably, the wet sealing foil material is in the form of a
spreadable paste, preferably, a thin paste or a thick slurry
consistency is utilised.
Preferably, the relative ratio of non-dry derived CEV to dry CEV in
the dried sealing foil is between 0.01:1 and 20:1, more preferably.
between 0.05:1 and 10:1, most preferably between 0.1:1 and 4:1.
Since CEV is a relatively expensive material compared with
gas-exfoliated vermiculite, eg TEV, in a non-spirally wound gasket
according to the invention, the resilient layer may also comprise
particles of gas-exfoliated vermiculite, eg the foil may comprise
particles of gas-exfoliated vermiculite bonded with the particles
of CEV. The material used may be milled or otherwise reduced in
particle size to a particle size of less than 50 .mu.m, however,
preferably, the particle size of at least a substantial proportion
is more than 50 .mu.m, preferably, 50-300 .mu.m, more preferably
50-250 .mu.m, most preferably 50-200 .mu.m. Other possible
additives include talc, mica and unexfoliated vermiculite.
By dry CEV is meant CEV having a moisture content of less than 20%
w/w, more preferably, less than 10% w/w, most preferably, less than
5% w/w.
Preferably, the CEV component in the wet material comprises a
mixture of dried CEV and CEV available in a slurry form. However,
it is necessary to use sufficient dried CEV to give an acceptable
solids content. A high solids content in the wet material assists
reduction in skinning in the subsequent drying process whilst
maintaining a high solids content in accordance with the
invention.
Preferably, the dry CEV is prepared by a suitable drying technique.
Suitable drying techniques include: cake drying and pulverising;
film drying and pulverising; rotary hot air drying; spray drying;
freeze drying; pneumatic drying; fluidised bed drying of partially
dried solid; and vacuum methods including vacuum shelf drying.
Preferably, any of the features or any preferred features of any
aspect of the present invention may be combined with the first
aspect and the reference to the first aspect in the method of the
second aspect should be interpreted accordingly.
When utilised, the hydrolysis resistant polymer may be coupled to
the vermiculite by a coupling agent.
In a gasket according to this preferred aspect of the invention, it
is found that the layer is more water resistant than a material
containing only vermiculite and a coupling agent and also more
water resistant than a material containing only vermiculite and a
polymer.
The coupling agent may be a silane, eg a vinyl functional silane
such as triethoxy vinyl silane
(CH.sub.3CH.sub.2O).sub.3SiCH.dbd.CH.sub.2.
It is also possible for the resilient material to comprise
unexfoliated (intumescent) vermiculite which can, on heating of the
gasket, eg in situ, form TEV to swell the resilient layer and, thus
improve sealing.
The resilient material may be bonded to the support layer by
adhesive but it may be advantageous if it is mechanically bonded.
Preferably, however, no adhesive is required.
In a gasket according to any aspect of the invention, it is found
that the particles of the plate-like filler when present, tend to
orientate themselves into the plane of the strip and act like a
large number of tiny leaf springs, thereby improving sealing.
In accordance with any aspect of the present invention the
plate-like filler may be selected from the group consisting of
talc, molybdenum disulphide, hexagonal boron nitride, soapstone,
pyrophyllite, milled thermally exfoliated vermiculite, mica,
fluoromica, powdered graphite, glass flake, metal flake, ceramic
flake, or kaolinites. However, a particularly preferred vermiculite
material is one with a plate size substantially in the range 50-300
.mu.m for example FPSV available from W R Grace & Co. FPSV is a
registered trade mark of W R Grace & Co.
In general, a plate-like filler has an average width of plates of
at least three times the average thickness.
The sealing layer may comprise 5-80%, eg 20-50%, by weight of the
plate-like filler, preferably, 25-40% of the plate like filler is
present in the dried sealing layer.
It is a still further object of any aspect of the present invention
to provide a gasket comprising a sealing foil based on exfoliated
vermiculite, which foil comprises a polymeric binder, the foil
providing improved sealing at temperatures at which the binder
degrades.
Optionally, the sealing foil of any aspect of the present invention
also comprises an intumescent material selected so that it expands
at temperatures at which said hydrolysis resistant polymer
degrades.
In a gasket according to this optional feature of the invention, at
temperatures which cause the binder to degrade, the intumescent
material expands to at least partially fill the void left by the
binder, thereby helping to maintain sealing.
Preferably, the intumescent material is unexfoliated vermiculite
because, after exfoliation, it has good heat resistance. Another
possibility is to use partially exfoliated vermiculite, ie
vermiculite which has been exfoliated at a lower temperature than
is normally required to fully exfoliate it. The unexfoliated or
partially exfoliated vermiculite may be treated (by methods which
are known per se) to reduce the temperature at which exfoliation
occurs, eg the temperature can be reduced to as low as 160.degree.
C. Other possible intumescent materials include expandable
graphite, sodium silicate, and perlite.
Preferably, the foil width is at least 10 cm, more preferably, at
least 20 cm, most preferably at least 30 cm. Especially preferred
are foils of width greater than 1 metre, for example 1.3
metres.
The intumescent material may form up to 50% by weight of the layer
but up to 20% is preferred.
In order that the invention be better understood, embodiments of it
will now be described by way of example.
There now follows a detailed description of illustrative examples
according to the different aspects of the invention.
Method A
The paste is prepared as follows (Z-Blade mixer):
TABLE-US-00001 Grace Microlite HTS Dispersion 18.07 kg Grace
Microlite PCEV Powder 9.49 kg Grace FPSV Powder 6.58 kg NBR
Solution * 6.10 kg Silquest Al51 Silane ** 0.19 kg NB - FPSV is
fine-milled TEV. * this is prepared in a Papenmaier high sheer,
high speed solution mixer; add 500 g NBR crumb to 2500 g toluene,
mix 5 min (max speed), add 31.3 g Perkadox BK 40B (peroxide curing
agent), mix 5 min further and then transfer into sealable
container. ** equivalent to 0.103 kg silane (ethanol solution).
a) Add all except silane and rubber solution. Mix 5 min. b) Add
silane and mix 5 min. c) Add NBR solution and mix 5 min. Dump into
clean plastic bag and seal in plastic tub. Variations on Method
A:
Latex based paste, also containing 5% by dry weight of NBR
incorporated in the form of water-based latex (40% solids) so that
2.50 kg of latex is equivalent to the 6.10 kg of rubber solution
(sample 5).
Polymer-free paste, in which the polymer has been omitted from the
above formulation (samples 1-4).
21/2% latex paste prepared by halving quantity of latex in sample 5
above (Sample 9).
FURTHER EXAMPLES
Two further samples were prepared as previously described, but
using a solvent-free variant of the paste based on nitrile latex
(Breon 1562 (NBR latex) -40% solids). This is mixed according to
the given cycle, substituting 1.02 kg of latex for the rubber
solution. The removal of the solvent is intended to allow paste to
be transported safely (particularly by air-freight).
METHOD OF APPLICATION
The paste needs to be applied in the form of a thick slurry
("buttercream" consistency) and is prepared by thinning the paste
formulations which are described below by adding water. Take 2
parts of paste (up to 2 kg) break up into handful sized lumps in a
clean container and pour over 1 part of water (by weight), stir to
a consistent texture. The preferred formulation for the paste
(without the additional water) is described below. An even coat of
paste which dries to approximately 0.6 mm thickness is applied to a
forming sheet thickness of up to 0.1 mm using a doctor blade set to
about 2 mm. The paste may be allowed to dry at room temperature,
whereupon the forming sheet is then removed to leave a film of
paste. The film in the form of a foil 124 mm wide by up to 5 m long
is then ready for use. Typically the foil is passed through
crimping rollers beforehand to make it more flexible.
In one method, the possibility is envisaged of driving the forming
sheet, so that it moves at a constant rate through the coating
device.
The CEV used was W R Grace's HTS dispersion which is approximately
15% solids. The dry CEV used was W R Grace's "Microlite Powder".
The FPSV was also obtained from W R Grace. The rubber used in these
examples was either nitrile rubber N36C80 from Zeon.
The reader's attention is directed to all papers and documents
which are filed concurrently with or previous to this specification
in connection with this application and which are open to public
inspection with this specification, and the contents of all such
papers and documents are incorporated herein by reference.
All of the features disclosed in this specification (including any
accompanying claims, abstract and drawings), and/or all of the
steps of any method or process so disclosed, may be combined in any
combination, except combinations where at least some of such
features and/or steps are mutually exclusive.
Each feature disclosed in this specification (including any
accompanying claims, abstract and drawings), may be replaced by
alternative features serving the same, equivalent or similar
purpose, unless expressly stated otherwise. Thus, unless expressly
stated otherwise, each feature disclosed is one example only of a
generic series of equivalent or similar features.
The invention is not restricted to the details of the foregoing
embodiment(s). The invention extend to any novel one, or any novel
combination, of the features disclosed in this specification
(including any accompanying claims, abstract and drawings), or to
any novel one, or any novel combination, of the steps of any method
or process so disclosed.
* * * * *